This invention relates generally to severing fibrous sheet material, particularly aerospace material of the type having side-by-side boron or graphite fibers in an epoxy matrix. More specifically, this disclosure deals with a novel method of cutting such oriented fibrous material with a notched blade so moved relative to the material that the upper and lower sides of the notch chop through the material along a line of cut which may be at any angle to the orientation of the fibers.
Notched blades are known from prior art patents such as U.S. Pat. No. 4,133,236 to the same inventor, and U.S. Pat. No. 255,358 to Warth. Sheet material cutting apparatus are also well known, indeed cutting heads capable of computerized control are commercially available. Such an apparatus is shown and described in U.S. Pat. No. 3,955,458 and U.S. Pat. No. 4,033,214 both issued to the inventor herein. Such units include a vertically reciprocating cutting blade suspended from a cutting head in a carriage capable of moving the head in a horizontal plane to cut material spread on a support surface. The head includes means for rotating the blade on its longitudinal axis in order to remain tangential to a desired line of cut and to be rotated in anticipation of a very sharp corner in the line of cut. In situ sharpening of such blades by devices incorporated in the head are also known, including blade sharpening devices capable of sharpening laterally skewed notches in the blade leading edge (See U.S. Pat. No. 4,133,236 for such blade sharpening devices).